Atmospheric and oceanic circulation altered by global mean sea-level rise

Over recent decades, the rate of global mean sea-level rise has increased, although the magnitude—tens of centimetres—remains small from a geological perspective. Such a modest rise in sea level presents a challenge when attempting to assess its global climate impacts, as the signal is weak. However, in previous warmer geological periods, sea levels reached up to tens of metres higher than the present levels. These palaeoclimate periods offer a unique opportunity to investigate the climate effects of higher sea levels. Here, using climate simulations of the Last Interglacial period and a set of present-day sea-level sensitivity experiments, we highlight the importance of global mean sea-level rise in modulating global climate. The lowering of terrestrial elevation and deepening of oceanic bathymetry due to a spatially uniform rise in sea level reorganizes atmospheric and oceanic circulations. Our simulations of the Last Interglacial show that considering this aspect of global mean sea-level rise in isolation from changes associated with land–sea masks or freshwater input reduces the long-lasting model–data mismatch in the Southern Hemisphere. Furthermore, the present-day sensitivity experiments demonstrate that a slight increase in global mean sea level causes substantial adjustments in the global climate, particularly at mid–high latitudes.